1. Field of the Invention
The present invention relates apparatus and device for alignment of wheels and axles vehicles, particularly trucks but also of trailers, buses and four wheel drive vehicles.
2. Description of the Prior Art
In the alignment of steer wheels of trucks and other vehicles it is known to attach a clamp to the rim of a steer wheel of a vehicle to be examined, said clamp having mounted thereon a short, directionally adjustable shaft which is directionally adjusted to be either parallel to or coincidental with the axis of rotation of the wheel under examination. Thereafter a light source is suspended from the shaft in association with a counterbalance device such that an image of a calibrated scale can be projected across the front of the vehicles; the image is then focused onto a flat surface on the far side of the vehicle.
Based on the position of the projected image on the flat surface on the far side of the vehicle, it is possible to calculate the alignment of the steer wheel under examination.
It is also known, in the investigation of rear axles of vehicles, to attach a directionally adjustable shaft to a non-steer wheel in the manner described above and to mount an axially rotatably light source thereon such that a light beam can be projected in any direction at right angles to the shaft. The light beam is projected onto a calibrated scale at the front of the vehicle, rotated through approximately 180.degree., then projected onto a scale at the rear of the vehicle. Based on a comparison of the points illuminated on the front and rear scales, the orientation of the axle, relative to the longitudinal center-line of the vehicle, can be calculated.
It is a requirement of such devices that they be adapted to be readily mountable and demountable from the vehicle under examination. The prior art devices have been found to be deficient in that when they are mounted on the directionally adjustable shaft, the interaction between the shaft and mounting means is such that the prior art devices are subject to slight variations in orientation from installation to installation. Consequently, in order that the light beam can be correctly projected and reliably interpreted, the prior art devices require calibration before each wheel is examined. Furthermore, as the devices need to be at least partially rotated during use, small movements occasionally occur in the connection means by which the light sources of the prior art devices are suspended. Thus, the prior art devices sometimes require recalibration during a wheel alignment examination.